This invention relates to a piercing valve for tapping pipelines and more particularly, to such a valve commonly used, for instance, in safely tapping a gas line of a refrigeration system for exhausting pressurized gas therefrom and recharging the same during repair operations. According to certain improvements of the present invention, a unique and simplified seal arrangement is provided between the valve assembly and the section of pipeline upon which the valve is mounted insuring complete sealing against the escape of pressurized gas other than through the intended transfer passageway between the valve and pipeline. Furthermore, according to certain other improvements of the present invention, an improved gripping and abutment between the valve and pipeline section is obtained which deforms the pipeline section into a shape permitting easier and more positive piercing thereof and also enhancing the foregoing sealing features.
Various similar forms of piercing valves for tapping pipelines have heretofore been provided, one of the principle uses being in the refrigeration repair industry. In the repair of refrigeration systems, for various reasons including the particular confined area of the refrigeration system installation, it is most frequently difficult, if not impossible, to gain access to the interiors of the various pressurized gas pipelines by normal disconnection procedures for the exhaustion of pressurized gas therefrom and the recharging of the same. For this reason, piercing valves for tapping such pipelines are commonly used by refrigeration repairmen, such valves being constructed capable of mounting over virtually any exposed pipeline section and having means incorporated therewith for piercing the particular pipeline to exhaust pressurized gas therefrom and recharge the pipeline system through a transfer passageway of the valve.
In general, such piercing valves have been comprised of assemblable blocks which may be assembled telescoping a pipeline section which is presented for convenient access. A piercing needle operably mounted in one of the blocks is then moved inwardly to pierce the particular pipeline section and upon opposite piercing needle movement, a communication is provided from the interior of the pipeline section through the pierced hole, through a portion of the piercing needle opening and into a transfer passageway of the valve block. In this manner, by exterior connection to the transfer passageway of the valve assembly, pressurized gas may be removed from the refrigeration pipeline system and the pipeline system recharged as is appropriate.
One of the major problems in the use of the prior piercing valve constructions has been of establishing a proper seal between the valve assembly and the particular pipeline section in order to prevent the leakage of pressurized gas from the valve assembly other than through the intended transfer passageway, that is, through the pierced hole of the pipeline section once established and outwardly along the outer circumferential surface of the pipeline section between the valve assembly and the pipeline section while the pressurized gas is flowing between the pipeline section interior and the intended transfer passageway of the valve assembly. The seriousness of this problem can be more greatly appreciated when it is realized that once the repair operations have been completed, there is no means of completely closing the pierced hole of the pipeline section so that the piercing valve that was used during the repair operations must be left assembled about the pipeline section and depended upon, once the transfer passageway is capped, to prevent pressurized gas leakage over a long period of time from the particular refrigeration pipeline system. Obviously, even if a minute unwanted pressurized gas leakage is permitted, the refrigeration system will ultimately fail.
One of the more common sealing means used in the prior piercing valves in an attempt to solve these sealing problems has been comprised of a pad of various types of sealing materials mounted against the valve block surface overlying the outer surface of the valve section to be pierced and surrounding the location of the ultimately pierced hole. In other words, in the piercing valve constructions, registering semi-circular grooves are formed in the valve block surfaces which are ultimately brought into abutment surrounding the valve section and with the valve section located in these grooves. Usually, the piercing needle is mounted in the valve upper block so that the sealing pad, usually consisting of a thin rectangular sheet of seal material, is mounted against the surface of the upper block within the upper block groove against the outer surface of the pipeline section surrounding the location of the ultimately formed pipeline pierced hole with compression between the valve blocks and the pipeline section outer surface depended upon to establish the sealing action over a relatively wide surface between the valve upper block and pipeline section.
In order to provide a completely operable sealing action, therefore, the grooves of the valve sections must conform quite closely to the contour of the pipeline section so that a relatively even seal material compression is maintained, otherwise leak paths will be established along the various surfaces. Furthermore, where shims are used, usually in the valve lower block groove, for adapting the particular piercing valve to a series of different pipeline diameters, the problem of establishing relatively even compression in this sealing action is even more greatly magnified. The overall result is that with the prior piercing valve constructions, the important sealing actions have been quite unpredictable and troublesome with frequent leakage failures.
A still further serious problem encountered with the prior piercing valve constructions has involved the pipeline piercing operation, the ultimate piercing of the pipeline by the piercing needle to provide the required communication between the pipeline interior and the transfer passageway of the valve. Unless exact alignment and secure positioning of the pipeline section by the piercing valve blocks is maintained, penetration of the piercing needle through the wall of the pipeline section can be inhibited and a difficult hole piercing operation results. In extreme situations, even slight deformation of the pipeline section can occur during this hole piercing operation which can even further complicate the foregoing sealing problems. This same pipeline deformation danger with its complicating results is even more possible where the securing of the piercing valve blocks causes a flattening deformation of the pipeline section at the area of intended piercing needle penetration since it is fundamental that the more flat the pipeline section wall against which the needle penetrating force is exerted, the less strength against deformation.